Treatment of polybutadiene



United States Patent 3,254,043 TREATMENT OF POLYBUTADEENE Gene F. Trott,Clarksville, Ind, assignor to American Rubber and Chemical Company, NewYork, N.Y., a corporation of Delaware No Drawing. Filed May 19, 1961,Ser. No. 111,162 1 Claim. (Cl. 260-27) This invention is concerned witha process for treating polybutadiene to improve its processibility. Inparticular, it is concerned with adding certain amines to polybutadienehaving at least about twenty-five percent (25%) cis-1,4 configuration sothat the plasticity of the material is reduced and it may be processedmore readily. It should be emphasized that, by means of the presentinvention, the plasticity is reduced while other physical properties arenot impaired, but are in some cases improved.

The present invention is useful in the treatment of stereospecificpolybutadiene containing at least about twenty-five percent (25%)cis-1,4 con-figuration. The plasticity of a polymer is a function ofseveral factors, among which may be mentioned molecular weight,molecular weight distribution, and various interand intramolecularforces. The amine additives of the present invention are believed toexert their influence by modifying the molecular forces, characteristicof cis-1,4 polybutadiene in the solid state, due to packing of themolecular chains.

The term plasticity is defined in the American Society for TestingMaterials Special Technical Publication No. 184 as being:

The property possessed by certain solid materials of keeping the shapeor form imparted to them by a deforming force. It is characterized by acomplete lack of elasticity and may be regarded as a state of matter inwhich internal friction and tendency to flow balance each other.

The plasticity of a polymer may be measured in several ways, the mostcommon method in the United States being the use of a Mooney viscometer.The use of this instrument is described in the A.S.T.M. Standards of1958, part 9, A.S.T.M. designation D92757T. The measure of plasticityobtained by using the Mooney viscometer is referred to as the Mooneyviscosity.

When a material has a high Mooney viscosity, it is difiicult to process.In particular, it is difficult to mill it or to extrude it. The presentinvention solves this problem by providing a method for lowering theMooney viscosity of (sis-1,4 polybutadiene. Furthermore, materialtreated according to the present invention emerges from a Garvey diewith a much better rating than untreated material. (The Garvey dieextrusion test is also described in A.S.T.M. Special TechnicalPublication No. 184.) The treated material emerges from the Garvey dietest with improved surface, edges, corners and contours.

Prior to the present invention it was often necessary to incorporatenatural rubber with cis-1,4 polybutadiene in order to obtain materialwhich could be readily proc essed. It is one of the very importantadvantages of the present invention that the use of natural rubber is nolonger required for this purpose.

Conventional cis-1,4 polybutadiene can not be milled on a roll mill athigh temperatures without great difiiculty. By the use of the presentinvention there are obtained materials which can be successfully andeasily milled at much higher temperatures. The invention therefore makesis possible to manufacture cis-l,4 polybutadiene having a Mooneyviscosity low enough to be consistent with easy processing, but havingwear resistance and other desirable properties in no way impaired.

The additives employed in the present invention are primary or secondaryamines containing at least six carbon atoms. The amines may bealiphatic, aromatic, cyclic, saturated or unsaturated. Both mono anddiamines may .be used. Best results have been obtained with unsaturatedcompounds. In general, primary amines are more effective than secondaryamines. Particularly good results have been obtained usingl-aminooctadecene- 9. As examples of other amines which are useful inthe present invention, there may be mentioned l-aminooctadecane,dehydroabietyl amine, dodecyl amine, ctyl amine, hexyl amine, distearylamine, dipalmetyl amine, dihexyl amine, and oleic-1,3-propylenediamine(which may also be used in the form of its monoand di-oleates). Thislast named amine is representative of a class of N-alkyl trimethylenediamines. Amines of this class give particularly good results,especially when the alkyl group contains from 12 to 18 carbon atoms.

In carrying out the process of the present invention, the amine is mixedwith the cis-l,4 polybutadiene at some stage after the desired degree ofpolymerization has taken place. This may be conveniently accomplishedwhile the polymer is in the reaction solution in which it has been made.The treated polymer is then recovered by conventional procedures.Although experimental evidence is not yet conclusive, in some cases anadditional advantage of the invention may be obtained by using anunsaturated amine as a shortstop to the polymerization reaction whichforms the polybutadiene. This would result in eliminating the need touse a conventional shortstop w-hich does not improve processibility.

The amount of amine to be added varies considerably. Some amines aremore effective than others, and some samples of polybutadiene requiremore amine than others. In general, it may be said that where thepolybutadiene has a relatively low Mooney viscosity to start with, lessamine will be required to bring about a noticeable reduction in theMooney viscosity. For example, as little as 0.2 of a percent may give anappreciable result. On the other hand, polybutadiene samples whichinitially have a high Mooney viscosity require more amine to bring aboutan appreciable lowering of the Mooney viscosity. As much as 1% amine maybe required in some cases. Percentages are stated by weight based on theamount of polybutadiene.

It has been observed that in general the lowering of the Mooneyviscosity reaches a maximum when a particular amount of amine has beenadded, and the subsequent addition of still more amine causes no morelowering of the Mooney viscosity. For most purposes, the optimum amountof amine to be added can be stated as being from, roughly, two or threepercent up to several percent. In the case of samples having'a very highinitial Mooney viscosity as much as ten percent may be used.

The following examples are given solely for purposes of illustration andare not to be deemed as limitation of the present invention, manyvariations of which well occur to those skilled in the art withoutdeparting from the spirit or scope thereof.

Example 1 200 grams of polybutadiene, containing approximately cis-l,4configuration, and having a Mooney viscosity at 212 F. of 42, wasdissolved in approximately 3% liters of toluene. 6 grams of oleyl aminewas then added to the polymer solution. The solution was stirred byhand. Steam was then injected into the mixture until nearly all of thetoluene had been stream distilled, after which the polymer-amine mixturewas dried on a hot 3 roll mill at approximately 200 to 220 F. The Mooneyviscosity at 212 F. of the treated polymer was 28.

It is thus seen that the Mooney viscosity was lowered from 42 in theuntreated material to 28 in the treated material. All Mooney viscositiesare base on large rotor readings.

Example 2 200 grams of polybutadiene, containing approximately 95%cis-1,4 configuration, and having a Mooney viscosity at 212 F. of 46,was dissolved in approximately 3 /2 liters of toluene. 6 grams ofdehydroabietyl amine was then added to the polymer solution. Thesolution was mixed thoroughly by hand stirring. Steam was then injectedinto the mixture until nearly all of the toluene had been removed, afterwhich the polymer-amine mixture was dried on a hot roll mill atapproximately 200 to 220 F. The Mooney viscosity at 212 F. of thetreated polymer was 33%.

In order to show further the effect. of dehydroabietyl amine on thepolybutadiene sample treated above, Garvey die data at 180 F. wereobtained on the untreated raw polymer containing 50 parts high abrasionfurnace carbon black (HAP), and on the treated raw polymer containingthree percent (3%) dehydroabietyl amine and fifty (50) parts HAF carbonblack. The Garvey die readings are reported in the following table:

It thus is seen that the treated polybutadiene scored better than theuntreated material in every part of the test.

4 Example 3 Using the procedures of the foregoing examples, tests wererun on many samples of polybutadiene, using various amines as additives.The tested polybutadienes included materials varying from abouttwenty-five percent (25%) to iniety-eight percent (98%) in their contentof cis-1,4 configuration. In all cases it was found that, when a primaryor secondary amine containing at least six carbon atoms was added in anamount from few tenths of a percent to several percent, the Mooneyviscosity was lowered and the Garvey extrusion index was increased.

What is claimed is:

A process for lowering the plasticity of polybutadiene containing atleast twenty-five percent cis-1,4 configuration, said process consistingessentially of incorporating in a solution of the polybutadiene a smallbut eifective amount of dehydroabietyl amine.

References Cited by the Examiner UNITED STATES PATENTS 2,234,204 3/1941Starkweather et a1. 260-32.6 2,592,708 4/1952 Kelly 26032.6 2,643,9816/1953 Kelly 26032.6 2,686,163 8/1954 Smith et al. 260-32.6 2,989,5136/1961 Hendry et a1. 260-5 .OTHER REFERENCES Marchionna: ButalasticPolymers, Reinhold Publishing Corp., New York, 1946, page 423.

Railback et al.: Rubber and Plastics Age, October 1958, pages 867874.

Wilson: British Compounding Ingredients for Rubber, W. Heifer and Sons,Ltd., Cambridge, 1958, page 287.

MORRIS LIEBMAN, Primary Examiner.

LEON J. BERCOVITZ, Examiner.

L. G. KASTRINER, D. W. ERICKSON, B. A.

AMERNICK, Assistant Examiners.

